An augmented reality (AR) sound technology is being studied in which a sound environment around a certain reference point is compiled with a limited number of virtual speakers (virtual sound sources) and the environment is reproduced at another point. In the AR sound technology, sounds from many directions (eight directions, for example) in the surrounding area are reproduced in another space, so communication bands are used to transfer many sound streams captured in each direction to a reproducing apparatus.
To distribute, for example, content from a server to a user terminal, a technology is used by which a large communication band on a network is assigned to a portion that attracts much attention from the user and a small communication band is assigned to a portion that does not attract so much attention from the user (see Japanese Laid-open Patent Publication No. 2011-172250, for example).
As described above, many communication bands are used to transfer many sounds. Therefore, it is difficult to use the AR sound technology in environments in which bands are limited, such as, for example, wireless local area networks (WLANs) and carrier networks.
To reduce the amount of communication data, lossless compression, lossy compression, or the like may be carried out on sounds to be transferred. In view of compression efficiency, lossy compression, in which sounds are compressed at a high rate, is preferable. In lossy compression, however, sound quality is lowered; if, for example, a high-frequency component, which is a key to determine the vertical direction of a sound source, is lost, perception of sound image localization at the forward of the user (auditor) is deteriorated. This causes a problem in that, for example, a sound at the forward of the users is heard as if it were heard from a position higher than a position assigned as a virtual sound source, making it difficult to obtain appropriate perception of sound image localization at the forward.